A heat exchanger may be used to provide for heat transfer from one medium to another. Heat exchangers may be used in a variety of application environments, such as refrigeration, air conditioning, power plants, petrochemical plants, petroleum refineries, gas processing, and sewage treatment.
A two-phase distribution (e.g., a distribution of both liquid and vapor) inside heat exchanger headers has posed a challenge. One environment in which such a challenge is present is in connection with evaporators of air conditioning units. Two-phase flow has been distributed using a closed-end tube with a series of holes in the side. An example of such a tube 102 is shown in FIG. 1. The tube 102 may include an open end 101, a closed-end 104 and a series of holes 106 between them. A two-phase flow may be inserted or injected into the tube via an opening. Such insertion/injection is shown via an arrow 108 in FIG. 1.
An assumption behind the tube 102 of FIG. 1 is that the flow of refrigerant entering the tube 102 at the open end 101 is annular and remains annular as it traverses the tube 102 towards the closed-end 104. If such an assumption held, a (near) uniform distribution of the two-phase refrigerant may be realized at the holes 106. In practice, the flow may tend to stratify as it traverses the tube 102 towards the closed-end 104. Such stratification may be a result of deceleration in the tube 102, and may be due to differences in mass between the liquid component and the vapor component of the two phases.
As a result of the stratification, the liquid component may tend to pool towards the closed-end 104 of the tube 102 in proximity to distal end holes 106a. Similarly, the vapor component may tend to pool and exit the tube 102 in proximity to the proximal end holes 106b. The non-ideal or non-uniform distribution of refrigerant that may be realized in actual practice may degrade the performance of the heat exchanger.
In order to address the issue of non-uniform distribution, the discharge holes 106 may be aligned at an angle, such as forty-five (45) degrees with respect to gravity. This approach, however, lacks robustness and is not universal for all operating conditions (e.g., quality and flow regimes).